TMS Glossary: Key Terms and Acronyms Explained

TMS therapy comes with its own vocabulary — protocol names, acronyms, billing terms, and regulatory language that can be confusing to someone encountering it for the first time. This glossary collects the terms most commonly used when discussing TMS, defined plainly and without evaluative claims about effectiveness or safety, so you can use it as a quick reference alongside the other articles on this site.

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TMS (Transcranial Magnetic Stimulation). A treatment that uses a magnetic coil placed against the scalp to deliver pulses that stimulate targeted regions of the brain. TMS is delivered in a series of sessions over a defined course of treatment.

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rTMS (Repetitive Transcranial Magnetic Stimulation). TMS delivered as a series of repeated magnetic pulses in a steady pattern over the course of a session, historically the most established way of delivering TMS. 

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iTBS (Intermittent Theta-Burst Stimulation). A patterned way of delivering TMS pulses in short rhythmic bursts, modeled on natural brain theta-wave activity, that compresses a session down to roughly three minutes rather than the longer session times associated with standard rTMS. See glossary-02-rtms-itbs-accelerated-terms-defined.md and clinical-05-itbs-vs-standard-rtms.md for more detail.

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Accelerated TMS. An approach that delivers multiple TMS sessions per day over a compressed number of days, rather than one session per day over several weeks. Accelerated protocols are generally made possible by the short session time of iTBS. See business-05-accelerated-tms-as-a-differentiator.md for how this protocol is discussed from a practice perspective.

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Motor threshold. The minimum intensity of magnetic stimulation needed to produce a small, observable movement (typically in the hand) when the coil is positioned over the corresponding area of the brain. Motor threshold is measured at the start of a course and used to calibrate the stimulation intensity used in treatment sessions.

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DLPFC (Dorsolateral Prefrontal Cortex). A region of the brain located toward the front and side of the head that is the common target location for TMS coil placement in depression treatment protocols.

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Coil. The device component placed against or near the scalp that generates the magnetic field used to deliver stimulation. Different coil designs (see figure-of-8 coil and H-coil, below) are built to target the brain in different ways.

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Figure-of-8 coil. A coil design shaped like two adjoining loops (resembling the numeral 8) that produces a more focal, precisely targeted magnetic field, commonly used for standard TMS protocols targeting a specific brain region such as the DLPFC.

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Diffuse coil. A coil design intended to reach deeper and broader brain regions than a typical figure-of-8 coil, used in certain TMS protocols. "Diffuse coil" refers to a category of deep-reaching coil designs rather than a single specific product.

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Neuronavigation. A system, often camera- or sensor-based, used to help locate and confirm the coil position over a specific target region of the brain and to help maintain consistent placement across sessions.

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Pulse. A single discharge of magnetic stimulation delivered by the coil. Pulses are delivered in patterns (steady or theta-burst) and in specific counts that define a session's stimulation dose.

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Session. A single treatment visit during which a defined number of magnetic pulses are delivered. Session length varies by protocol, generally ranging from about three minutes for iTBS to closer to 20–37 minutes for standard rTMS.

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Treatment course. The full series of sessions prescribed for an initial round of TMS treatment, commonly delivered daily on weekdays over a period of weeks, or compressed into a period of days under an accelerated protocol.

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Maintenance TMS. Additional TMS sessions delivered on a less frequent schedule after an initial treatment course is complete, intended to sustain the effect of the initial course. Maintenance schedules are determined by the treating clinician on a case-by-case basis.

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Treatment-resistant depression (TRD). A term used to describe depression that has not responded adequately to a defined number of prior treatment attempts, such as antidepressant medications. Payers commonly use documentation of this history as part of coverage criteria for TMS, discussed further in regulatory-06-cpt-codes-reimbursement-tms.md.

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Prior authorization. A requirement, set by many insurance payers, that a clinic submit documentation justifying medical necessity and receive approval from the payer before treatment begins, rather than billing for treatment after the fact.

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CPT code. A standardized billing code (Current Procedural Terminology) that describes a specific medical service for claims and reimbursement purposes. TMS is commonly billed using codes in the 90867–90869 family; see regulatory-06-cpt-codes-reimbursement-tms.md for how each code is used.

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510(k) / FDA-cleared. A regulatory pathway through which a medical device manufacturer demonstrates to the FDA that a new device is substantially equivalent to an already-legally-marketed device. A device that has completed this pathway is described as "FDA-cleared," which is a distinct regulatory status from "FDA-approved." See regulatory-01-fda-cleared-vs-fda-approved.md and regulatory-02-how-tms-devices-get-fda-clearance-510k.md for a full explanation of this distinction.

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Indication. The specific condition or use for which a device or treatment has received regulatory clearance. A device's clearance is specific to its stated indications; see regulatory-03-what-indications-cleared-how-to-verify.md for how to verify what a specific device is cleared for.

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HSA / FSA (Health Savings Account / Flexible Spending Account). Tax-advantaged accounts that can generally be used to pay for qualifying medical expenses, including TMS prescribed for a diagnosed condition. See money-01-using-hsa-fsa-for-tms.md for more detail.

Frequently Asked Questions

What is the difference between rTMS and iTBS? Both describe ways of delivering TMS pulses. rTMS uses a steady repeating pulse pattern over a longer session, while iTBS uses patterned bursts that compress a comparable session into about three minutes. See glossary-02-rtms-itbs-accelerated-terms-defined.md for a fuller comparison.

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Is "FDA-cleared" the same as "FDA-approved"? No, these are distinct regulatory terms describing different pathways and standards. See regulatory-01-fda-cleared-vs-fda-approved.md for a full explanation.

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What does motor threshold mean, and why is it measured? Motor threshold is the minimum stimulation intensity needed to produce a small observable movement when the coil is positioned correctly. It is measured at the start of a course to calibrate the intensity used in treatment.

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What is the difference between a treatment course and maintenance TMS? A treatment course is the initial series of sessions prescribed to begin treatment. Maintenance TMS refers to additional, less frequent sessions delivered afterward to help sustain the effect of that initial course.

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Where can I find definitions specific to accelerated TMS terminology? See glossary-02-rtms-itbs-accelerated-terms-defined.md, which focuses specifically on distinguishing rTMS, iTBS, and accelerated TMS.

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Does this glossary make any claims about how well TMS works? No. This glossary is intended as a neutral reference for terminology only. Questions about clinical effectiveness or whether TMS is appropriate for a specific individual should be directed to a qualified clinician.

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This glossary is for general educational purposes only and does not constitute medical, legal, or financial advice.

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